238 Intelligence and Miscellaneous Articles. 



If, now, both gases have initially equal pressure, a change is soou 

 produced therein by diffusion. The hydrogen penetrates through 

 the porous piston more quickly than the oxygen ; hence the amount 

 of gas present on the hydrogen side diminishes, while that on the 

 oxygen side increases. This produces a lessening of pressure on 

 the hydrogen side, and an augmentation of pressure on the oxygen 

 side, so that the piston can be put in motion with a certain force, 

 and mechanical work performed capable of being made useful ex- 

 ternally. At the same time, with the movement of the piston the 

 gas on the side where it expands becomes cooler, and becomes 

 warmer on the side where it is compressed ; and consequently heat 

 passes over from a colder to a hotter body. 



These two circumstances, that work is gained in the process 

 without there being any difference of temperature present initially, 

 and that simultaneously heat also passes over from the colder divi- 

 sion into the hotter, are regarded b} r Mr. Preston as contradicting 

 the second proposition of the mechanical theory of heat. 



To this inference I cannot assent. If the conversion of heat into 

 work and the transference of heat from the colder to the hotter 

 body had taken place in such manner that the variable material at 

 the end of the operation were found in its original state, so that we 

 had to do with a cyclical process, then certainly there would be in it 

 a contradiction to the second proposition of the mechanical theory 

 of heat. But the matter does not stand thus. We have, in the 

 process, as variable material the two gases. These are at the com- 

 mencement unmixed, and at the conclusion mixed ; and therefore an 

 essential change has taken place with them, which may be regarded as 

 a compensation for the conversion of heat into work and the trans- 

 ference of heat from a colder into a hotter body. Since the gases, 

 through the molecular motion which we call heat, tend to mingle, 

 and indeed in such wise that the higher the temperature the more 

 quickly does the mixture result, we have here to do with an action 

 of heat comparable to the expansion of a gas by heat ; and hence 

 we must ascribe to the mixed gases a greater disgregation than to 

 the unmixed. Now, since the increase of disgregation is a positive 

 change, it may be compensated by the transformation of heat into 

 work and the transference of heat from a colder into a hotter body, 

 both of which are negative changes. 



It is therefore evident that, although it is true that the present 

 case possesses certain peculiarities by which it is superficially di- 

 stinguished from other cases, yet in the essential points with which 

 we are concerned in the mechanical theory of heat it is in complete 

 harmony with the cases usually treated, and contains nothing con- 

 tradictory to the second proposition of the mechanical theory of 

 heat. — Wiedemann's Annalen, 1878, pp. 341-343. 



ON MOSANDRUM, A NEW ELEMENT. BY J. LAWRENCE SMITH. 



Having read the interesting communication from J\l. J.-L. Soret 

 to the Academy relative to the absorption-spectrum of the gadolinite 



